The present invention relates to enteral pumps for delivering liquid nutrition to patients who are unable to eat.
Enteral feeding pumps are used to supply liquid nutrition to patients who are unable to eat. The pumping system generally consists of the pump and a disposable tubing set for delivery of the liquid nutrition. The tubing set is connected between a bag of liquid nutrition and a patient's gastric line. A section of the tubing set is seated on the pump housing where a rotor draws fluid through the tubing set by peristaltic action.
A common design feature of enteral pumps is the ability to detect the presence or absence of liquid flowing through the tube set. This is typically accomplished by the detection of drops falling within a transparent drip chamber portion of the tubing set. In this regard, the transparent drip chamber is seated within an opening in the pump housing where an infrared (IR) light source (light emitting diode—LED) and infrared detector are positioned on opposing sides of the drip chamber transverse to the liquid flow. The IR beam passes through the drip chamber. When a drop of liquid falls, it interrupts the IR beam and this interruption is converted to an electronic pulse. The pulse presence and frequency are processed by the pump firmware, which then either allows continuing pump operation or stops the pump indicating one of several possible alarm conditions, such as occlusion or excessive flow.
For the drop detection system to operate reliably, the IR beam intensity must be set to a level that is sufficient to “see” through the drip chamber walls, but not so intense that that the beam is detected through the water drops without producing a detection pulse. The IR beam power level is optimized for water, since excess power can cause the water to be transparent to the infrared beam, i.e. the beam is strong enough to pass right through the water drop. Liquid nutrient is more optically opaque and thus it can be detected with a wider tolerance of beam power level. Because of this, water is the “standard” for calibration of the detection power. For current pump design, the beam power level is set to a fixed value that is intended to accommodate all variations in electronics and materials used in the beam path.
False alarms are an undesirable consequence of fixed sensitivity when the transparent wall of the drip chamber may become less transparent through the accumulation of liquid residue or droplets. These droplets are only a problem when they are located in the path of the IR beam. Given enough operating time, it is probable that a droplet will be situated in this manner. This issue is more problematic for water due to its propensity for droplet formation due to its high surface tension. Liquid nutrient has a relatively lower surface tension and droplets dissipate more readily once they impinge on the chamber wall. Water however, has a tendency to stay in place longer and thus create a blocking condition. With fixed infrared detector sensitivity, water droplets will cause false alarms.
Typically, enteral pumps deliver only liquid nutrient to the patient. In addition to the liquid nutrient, caregivers must also give water to the patient, as the liquid nutrient contains insufficient water for normal dietary requirements.
Several enteral pump manufacturers have produced pumps, which are capable of pumping both liquid nutrient and water from separate containers. A typical prior art design uses two separately programmable peristaltic pumping motors, which are activated according to a user program. Another method uses a single peristaltic pump, and a tubing set having an integral two-way valve. This valve is actuated by a second motor on the pump, and thus controls that liquid source. Both of these configurations are relatively high in cost because of the multiple motors.
In view of the foregoing, there is a desire for a less expensive enteral pump system that includes only a single motor as well as a method of operating an infrared drip sensor in an enteral pump system to reduce occurrence of false alarms. It is also desirable to provide a method of operating the infrared drip sensor that automatically adjusts the infrared beam power according to the current optical conditions. Further it is desirable to have a method of automatically adjusting the infrared beam power of an enteral pump system to accommodate water droplets and residue within the drip chamber. Even further still it is desirable to have a method of operating a drip sensor that can automatically distinguish between water flow and liquid nutrient flow.